I actually use the full relay lists (inboxes/outboxes from the user and their follows, favorites, local cache relays, blocked relays, relay hints, referenced relays, seen-on relays, http relays, default relays, etc.), in addition to adding 5 random relays for each publish. I do it all. There's no way to do "more outbox", it's just that I sometimes close connections. I don't keep all 300 or 500 or whatever open, constantly. It depends upon the context.